Obtaining samples of molten metal for laboratory analysis has been a problem confronting metallurgists for many years. Since the introduction of the basic oxygen furnace for the refining of steel with its relatively short refining time, there has been greater emphasis on immersion samplers in which the sample chamber or mold is directly immersed in the molten metal to be sampled.
Commercially available samplers generally fall into one of two categories; side-fill or end-fill. In the side-fill type the molten metal enters the sampler chamber through a passageway located in the sidewall of the sampler at or near the upper end of the sampler chamber when the sampling device is immersed in the molten metal. With such a filling arrangement there is no possibility for the molten metal sample to run out of the sampler chamber even though the sample is still in its liquid state when the sampling device is withdrawn from the bath of molten metal to be sampled.
An end-fill sampling device has its passageway to the sampler chamber located in the immersion end wall of the sampler chamber or in the side wall at or near the immersion end wall. The end-fill sampling device is preferred over the side-fill type by some because the molten metal entering the passageway in the immersion end of the sampling device is considered to be more representative of the molten metal in the bath and less likely to be contaminated by the material used in accomplishing the immersion of the sampling device.
When an end-fill sampler is immersed in a bath of molten metal the metal flows into the sampler chamber through the passageway. Because of the temperature and mass of the sampling device the sample of molten metal begins to cool and solidify in the passageway and sampler chamber and the sampling device may be removed from the molten metal bath with the sample remaining in the sampler chamber.
The end-fill sampling device, however, may experience a loss or run out of the sample upon withdrawal from the bath of molten metal if the metal in the passageway and/or the metal in the bottom end of the sampler chamber has not solidified before the sampling device is withdrawn from the bath of molten metal. This tendency to a run out of the sample is greatest when either the bath of molten metal has a high degree of superheat or the sampler chamber is large or both.